ag14+@andrew.cmu.edu (Albert H. Gough) (11/26/89)
Thanks to all who responded to my original posting. I have read TN 176 as recommended and I understand that Apple was unable to predict the changes implemented in the 4 Mb SIMMs, but even if I get 4 Mb SIMMs made of 1 Mb chips they will not work because the MacII ROM "will not recognize 4 Mb SIMMs". It seems to me this is a ROM bug that has nothing to do with the new chip design. Judging by the response, Apple has done an excellent job of emphasizing the 'we can't predict the future' explanation and playing down the mysterious ROM problem. Bert
rob@uokmax.ecn.uoknor.edu (Robert K Shull) (11/26/89)
In article <0ZPrKQq00WB48UuFcB@andrew.cmu.edu> ag14+@andrew.cmu.edu (Albert H. Gough) writes: >get 4 Mb SIMMs made of 1 Mb chips they will not work because the >MacII ROM "will not recognize 4 Mb SIMMs". It seems to me this is >a ROM bug that has nothing to do with the new chip design. Perhaps Apple could offer the ROM/SWIM upgrade without requiring purchase of the SuperDrive? This might make people a LITTLE happier (not much, read below).. BTW, summary of TN176: 4 meg SIMMs, produced from either 1 mbit or 4 mbit DRAMs, won't work in a Macintosh II due to an unspecified problem in the ROM startup code. 4 meg SIMMs, produced from 1 mbit DRAMs, should work in a IIx or a ROM-upgraded II. 4 meg SIMMs, produced from 4 mbit DRAMs, will NOT work in a IIx OR a ROM-upgraded II. This is due to the addition of an unanticipated extra test mode and addition of new meaning to a particular control line on the DRAMs. 4 meg SIMMs, produced from either 1 mbit or 4 mbit DRAMs, should work on SE/30, IIcx, and IIci. The note also says that modification of the SIMM (by adding an IC to insure the new mode doesn't get triggered) should allow IIx or ROM-upgraded IIs to work with 4 meg SIMMs using the 4 mbit DRAM. Unfortunately, this is bound to mean $$ (my opinion) if only the Mac II and IIx need this special SIMM. The note concludes by saying that there are no plans to recall, upgrade, OR change the design of the machines which exhibit this problem. Apparently the currently-being-produced IIx's still have the problem. Robert -- Robert K. Shull rob@uokmax.ecn.uoknor.edu chinet!uokmax!rob